Designing Hot Working Processes of Nickel-Based Superalloys Using Finite Element Simulation

Abstract

Knowledge of correct flow stress curves of Ni-based alloys at high temperatures is of essential importance for reliable plastomechanical simulations in materials processing and for an effective planning and designing of industrial hot forming schedules like hot rolling or forging. The experiments are performed on a computer controlled servohydraulic testing machine at IBF. To avoid an inhomogeneous deformation due to the influence of friction and initial microstructure, a suitable specimen geometry and lubricant is used and a thermal treatment before testing has to provide a microstructure, similar to the structure of the material in the real process. The compression tests are performed within a furnace, which keeps sample, tools, and surrounding atmosphere on the defined forming temperature. The uniaxial compressions were carried out in the range of strain rates between 0.001 and 50s−1 and temperatures between 950 and 1280°C. Furthermore, two-stage step tests are carried out to derive the work hardening and softening behavior as well as the recrystallization kinetics of the selected Ni-based alloys. At the end of this work a material model is adapted by the previously determined material data. This model is integrated into the Finite Element program LARSTRAN/SHAPE to calculate a forging process of the material Alloy 617.

Modeling the Flow Behavior of a High‐Manganese Steel Fe‐Mn23‐C0.6 in Consideration of Dynamic Recrystallization

“…To model the flow behavior, equations based on the work of Luton and Sellars 17–22 were adopted and combined with a special microstructure tracking algorithm. Although the model is based on empirical and phenomenological ideas, the validity of the constitutive equations (summarized in Table 2) used in the model was often confirmed and the model is widely applied due to its mathematical simplicity, uncomplicated parameter identification and the easy handling 23–31. The model was implemented as a FORTRAN subroutine coupled with the FEM‐Code LARSTRAN/shape.…”

Uniform Hot Compression of Nickel-based Superalloy 720Li under Isothermal and Low Friction Conditions

“…In this system, the workpiece, tools, and surrounding atmosphere could be maintained at a constant forming temperature. [6][7][8][9] The heatinsulated chamber was very effective at obtaining accurate flow stress; however, data related to the evolution of the microstructure could not be obtained because the workpiece could not be rapidly quenched. The second type of apparatus used direct-current heating in a Gleeble thermomechanical simulator.…”